Process for the sterilization of liquids



Jan. 15, 1935. V G. A. KRAUSE I PROCE5S FOR THE ST ERILIZATION OF LIQUIDS- Filed Ju ly 25, 1929 2 Sheets-Sheet 1 M'ausc Q Jan. 15, 1935. G, A, KRAUSE I 1,988,246

PROCESS FOR THE STERILIZA'IIQN OF LIQUIDS Filed July 25, 1929 2 Sheets-Sheet 2 E147 J5 E g' i5 1 JL fig 47a INVENTOR r tested Jan. 15, 1935 PROCESS FOR THE STEBILIZA'IION 0F LIQUIDS Georg Alexander Kranse, Munich, Germany, assignor to Katadyn, Inc., Dover, Deb, a corporatlon of Delaware Application July 25,1929, Serial No. 880.901 1 In Germany August 2, 1928 'IClalms.

This invention relates to a process tor the complete or partial sterilization of liquids by bringing them into contact with metals or metal compounds having an oligodynamic action; and aims at enabling the sterilization of the liquids tobe carried out whilst employing smaller amounts 0! oligodynamically active substance than were hitherto required.

' Processes of sterilizing liquids are already known in which metals or metal compounds having an oligodynamic action are employed. These known processes are carried out by bringing the liquids to be sterilized into contact with the 01180- dynamically active substances and leaving them in contact therewith until the said liquids become sterile. Since metals and metal compounds of the heavy metal group, inter alia also copper, antimony and the precious metals, silver, silver oxide, gold, iridium, thallium and others are em- 'pioyed with advantage for oligodynamic sterilization, the installation costs for olig'odynamic sterilizers constructed with these metals are very high, especially in the case of installations dealing with large amounts of liquid to be sterilized.

It has now been round that any desired amounts of liquid can with certainty be sterilized or partially sterilized to the required degree whilst using much smaller amounts of olig active metals than has hitherto been the case, by interrupting the contact between the liquids to be sterilized and the oligodynamically active substances prior to the complete sterilization; this preliminary sterilization being i'ollowed by a final sterilization which may, if desired, be of a multistage character.

It has in fact been ascertained that the partially sterilized liquids are automatically further sterilized without subsequent contact with oligodynamlc substance. 'I'hefinal sterilization tollow-.

i of a subsequent or intermediate auto-sterilisation.

. The complete sterilization process is thus terminated within ashorter or longer period according to the intensity of the initial, treatment.

Instead, of following the preliminary-sterilize tion with asingle or multi-sta'ge final sterilisation with oligodynamicaliy active substances of coarser consistency or less eilectlveness or in smaller amounts than employed lor the preliminary-sterilization it is also possible when necessitated by special circumstances to follow the preliminary sterilization by a single or multi-stage final sterilization by means of oligodynamically active substance of a greater effectiveness or in a finer state of division or in'larger' amounts than einployed iorthe preliminary sterilization and on occasion with a subsequent or intermediate auto-sterilization.. It is also possible to add non-sterile untreated liquid to liquid which has been preliminarily or completely sterilized in accordance with the invention, which is .then finally sterilized together with the preliminarily sterilized liquid.

Numerous types oi apparatus are suitable for carrying out the process of the present invention, provided that the same allow of a division 0! the sterilization into at least two stages, namely, a

preliminary sterilization and a final sterilization or into more than two stages, namely preliminary sterilization, intermediate sterilisation, carried out onoccasion in several stages; and final sterilization. Thus, for example the process maybe carried out in at least two sterilizing chambers arranged in series which are furnished with oligodynamically active substance or difierent degrees 0 eii'ectiveness which canbe for example, of. greater or lesser intensity or with oligodynamically active substances oi the same degree of intensive action but which are in diilerent states of subdivision for example, graduated coarser or finer division. The chambers may also be provided with varying amounts i. e. smaller or larger, amounts of oligodynamically active substance. I! desired, one or more or the sterilizing chambers subsequent to the first sterilizing chamber-tor example, the last sterilizing chamber-may serve for the autosterilization of the liquid which has already-come into contact with oligodynamically active substanceand which is free from oligodynamieany active substances. r

In these arrangements, one or more of the sterllizing chambers arranged in series, may be multiplied and arranged in parallel. similarly, ollgodynamically active be present in one ormoreotthe sterilixingchambersingraduatedamountsorinastateotgraduatedsubdivisionorinamountshavlhtagraduated elect. It is also possible however, to operationbyeitectingthesterilisaticninasins'lestuilix'ingchamberwhiehisprov'idedwitholigody active substance in a state of graduated division or in graduated amounts orin amounts a graduated action so that all the individualsterilizingstagesobtaininalinglcsterililinl -chamber.

The sterilization process of the present inventionmaybecarriedoutinacontinmintcrmittent or semi-continuous thus for ex-' ample, the preliminary sterilizer the'final sterilizer may operate diseontinueusly'or the pre- 9 or vice versa.

Moreover a preliminary sterilizer may co-operate with several final sterilizers or several preliminary sterilizers'may co-operate with one final sterilizer and'the like. Moreover the same liquid may be caused to run several times through the same preliminary sterilizer or final sterilizer or through both before it is conducted further. It is essential in carrying out the invention that the liquid to be treated leaves the preliminary sterilizing stage before it has reached the desired degree of sterilization whereupon it issubjected to a final sterilization which may be eiIected or aided by the auto-sterilization of the liquid issuing from the. preliminary sterilizing stage. Since, as is well known, the sterilization of liquids by bringing same into-contact with oligodynamically active substances can be controlled selectively, it 'is possible for example, to kill off all the pathogenic micro-organisms by the preliminary sterilization and, if a completely sterile liquid is to be obtained, to remove the still living micro-organisms by the final sterilization.

It is also however sumcient if only a part of the pathogenic micro-organisms are killed of! by the preliminary sterilization and all the pathogenic micro organisms are killed off by the final sterilization, whereas harmless spores may still remain alive in cases where it is necessary to remove from the liquid only the pathogenic spores.

Similarly the oligodynamic sterilization can be influenced or controlled in known manner by agitating the liquid or blowing in air or other gases as well as by adjusting the temperature in any one or in all of the sterilizing stages. Moreoverthe liquid may be exposed tolight or radiation, or subjected to the influence of electric currents, in any one stage during, before or after the sterilization.

. Similarly the liquids may be subjected to a filtration which may be efiected before the sterilization, between the individual sterilizing stages or after sterilization.

.In order more clearly to understand the invention, reference is made to the sec drawings which illustrate ditically anby way of example, several apparatuses suitable for carrying the invention into practical eifect.

In said drawings:- Fig. 1 illustrates a drop-filter constructed in accordance with theinvention;

' m. 2 shows a'sterilizing installation having a single sterilizing chamber for the multi-stagesterilization;

Fig. 3 shows. a sterilizing installation comprising a container which is divided into two separate sterilizing chambers.

Fig. 4 shows a sterilizing installation comprising two separate sterilizing chambers arranged in separate containers.

Flgs.5a,b,canddare :1 iclayoutsof v diflerent types of sterilizing installations.

to The drop-filter illustrated inFlg. 1, consists of a container 1 with a superimposed funnel: which is provided with a filter candle 3. The funnel 2 is filled with oligodynamically active substance 4. for example with silver, copper, silver oxide or the like precipitated on ,clay chips or the like.

As is well known, the filter candle 2 allows bacteria contained in the liquid to be treated, (for example impure water) to sprout through the filrs ter after a short time. Since however the liq has been preliminarily treated by contact with the oligodynamically active substance 4, the filtrate is completely sterilized by auto-sterilization after standing for some time in the vessel 1.

The sterilizing installation illustratedin Fig. 2

comprises a single container 5 filled with Raschig rings 6 of diflerent size which are provided with coatings of oligodynamically active substance for example, silver, iridium, or the like, for example by means of the metal spraying process.

Between the inlet 7 for the liquid to be sterilized and the outlet 8 the sterilizing chamber is divided into three stages 9, 10 and 11 insofar as larger or smaller Raschig' rings or thinner or thicker metal coatings or more active or less active oligodynamically active substance such as for example, amorphous silver, a mixture of amorphous and crystalline silver and crystalline silver being employed.

Fig. 3 shows a container 12 which is divided by a partition 13 into'two sterilizing chambers 14 her 14 into the chamber. 15 which may be pro-- vided with partitions 20, before it runs out through the outlet 18 is so controlled that on leaving said outlet the liquid the desired degree of sterilization. Similarly, the amount of oligodynamically active filling substance 16 inthe chamber 14 is so adjusted to the nature of the liquid to be treated that the latter is 01130- dynamically treated with sufllcient intensity to ensure that the final sterilization is terminated on passing through the chamber 15. It is moreover possible to adjust the relative capacities of the chambers 14 and 15 to the amount of the liquid and to the type of oligodynamically active substance employed by displacing the partition 13.

Fig. 4 illustrates an embodiment of an apparatus comprising a preliminary sterilizer 22 which is partially or completely filled with oligodynanlically active metals 21, such as for example silver, copper, silver-copper alloy spread on carriers, suchas quartz sand, and, which is ii. desired, of a multi-stage type. (Fig. 2) and which is provided with inlet 23. separated from the final sterilizer 24 having an outlet 25 for the treated liquid. The preliminary sterilizer andthefinalsterilizermayoperate either continuously or intermittently in the same way either one of the two sterilizers which are connected together by conduit 28 provided if Said preliminary sterilizer 22 is desired, with closure valve, may operate continuconnected with three final sterilizers 28. Fig. 50' .shows four preliminary sterilizers 29 combined with a single final sterilizer 30. Fig. 5c shows a preliminary sterilizer 31 which is connected with a finalsterilizer 33 by way of an intermediate stage 32. Fig. 5d shows two prelimina y sterilizers 34 which are connected byway of an intermediate' stage 35 with three final sterilizers 36. Any desired number of further systems of connections may be made in a similar manner.

- Example I 300 grams of quartz sand are coated with 30 grams of silver by wetting samewith a silver 1 metals.

nitrate solution and thereupon heating in a muflle furnace at 400 C. The quartz sand is placed in a suction-filter and 5 litres of water are passed therethrough per minute. The water is inoculated with half a million of the Bacilli coli communis per cubic cm. The water issuing iromthe filter which does not completely filter out the bacteria, still contains 15,000bacilli per cubic cm. The water is thereupon left to stand in a container in which no oligodynamically active metals are present and after hours sterility has ensued.

Example If complete to kill these yeast cells after the beer has been left to stand for two days in a vessel which con.- tains no further quantities I or oligodynamic Example IYII I Water containing 2,000 oi the Bacilli coli oommu'nis per cubic cm. was drawn through copper filings at a rate'oi' 500 cubic cm. per minute. -The water which had been thus treated contains only 400 bacilli per cubic cm. litter the water had been left to stand in a vessel containing no copper it was-found on testing same 12 hours after the water had passed through the filter, that it no longer contained any Bacilli coli communis.

Example IV were intended to sterilize water contain- I! it ing the same number of bacilli perv unit volume as in Example I completely during the contact with silver, it would be necessary to use about 5 grams of silver per litre of water. The duration or contact would amount to between '4 to 5 hours. Consequently the amount of silver to be prepared for the treatment of 1500litres of water would -be 1,500 grams or silver which would have to remain in contact with the water for 5 hours.

The same amount or water could be preliminarily sterilized within the same period with 30 grams 01' silver in accordance with Example I to such an extent that it would be completely autosteriliz ed within about 10 hours. a v

Consequently, when operating in accordance with the invention with 30 grams of silver the same eilect can be obtained as when operating according to known methods with 7,500 grams.

What I claim is: a

l. The method of ollgodynamic sterilization of liquids, which comprises dividing the sterilization into two periods and during the first period contacting the liquid with a relatively amount oi olig active material for a period of time to effect. incomplete sterilization oi the liquidmnd during the second period holdthan one-half the .amount'ot'o' ilization or-me liquid during the period'ot contactwiththeoiisodrnjlmicmaterMandstoring the liquid out of contact with the oligodynamically active material until the liquid has become. completely sterilized. I

, 2."!he method of oligodynamic sterilmation which comprises passing a liquid to be sterilized active material necessary'toeilectplete ring said liquid before use for a period of time suflicient to permit it to become completely ster-' ilized by auto-sterilization.

3. The method of oligodynamic sterilization which comprises contacting a liquid to be sterilized with an amount of oligodynamically ac tive material which is less than one-hali'the amount which will be used to give complete sterility to the liquid during the period of contact permitted, subsequently contacting the liquid with other oligodynamically active material, the

two bodies of oligodynamically active material being insumcient to givecomplete sterility-to the liquid during the period of contact permitted, and permitting a period oi! time to elapse before using the liquid to complete the sterilization by auto-sterilization.

4. 'nieprocess oi sterilizing liquids which comprises initially contacting the liquid to be sterilized with an oligodynamically active element insufllcient in amount to effect the final desired degree of sterilization during the period of contact, subsequently contacting said liquid with an oligodynamically active materialhaving a less activity than the activity of the original material and subsequently permitting the liquid to stand to complete sterilization of the liquid by auto-sterilization.

5. A process for sterilizing liquids which comprises the steps of preliminarily contacting said liquids with an amount of oligodynamicall'y active elements to cause incomplete sterilization and subsequently contacting said liquid with a more active oligodynamic substance than employed in the preliminary sterilization, the quantity oi. oli ody amicall n active element in the first step being less than the amount of the second step, and the amount of oligodynamically active substance in the second step being less than sufllcient to eflect the complete sterilization during the period of contact.

to a prede- 6. In the sterilization of liquids termined degree with oligodynamically active material the improvement comprising eflecting the said sterilization in at least two stages including an initial partial sterilization in the presence of andby contact with a body of oligodynamically active material and a subsequent auto-sterilization in the absence of said body oi material, whereby the said predetermined degree of sterilization is accomplished, the sterilization accom-' plished by contact of the liquid with oligodynamic material being insufilcient to accomp the predetermined degree of sterilization.

tact with the oligodynamic material. and;stor--.

ing said liquid in contact with a relatively small amount or oligodynamically active metal until the liquid becomes completely sterilized, the amount oi oligodynamically active metal uti-., lined in the final storage period being insuiiicient,

during its period or contact with the liquid, to

contribute appreciably, to the increase in jstee -'rility oi the liquid, the. completion of the sterility beingattributable essentially to autos'teriliaation eflected'by lapse oi. time.

. *GEORG manna muss. 

